1. Field of the Invention
This invention relates generally to photography, and more particularly to an electronic strobe flash apparatus for automatically producing a full flash light output in low ambient light, and a reduced amount of light output for fill-in flash in bright ambient light.
2. Description Relative to the Prior Art
The so-called computer or quenchable electronic strobe flash unit produces a predetermined amount of flash that generally corresponds to a desired exposure. This is commonly called a full flash mode of operation. In this mode, the amount of flash light output is regulated substantially independently of the ambient light intensity.
However, it is desirable to provide flash illumination to soften dark shadows in a scene photographed in bright ambient light. This illumination is commonly called fill-in flash. If bright ambient is not properly taken into account during a flash exposure, a fill-in flash picture can be overexposed. This can be particularly troublesome for a photographic process that uses a film having a narrow "exposure latitude" and which might be used in self-processing cameras.
U.S. Pat. Nos. 4,023,187 and 4,192,587 describe cameras having respectively, a flashlamp and an electronic strobe flash unit, which are fired under conditions of substantially high ambient light intensity to produce fill-in flash exposures. A selected portion of a desired exposure is attributable directly to ambient light while the remaining portion of the exposure is attributable predominately to fill-in flash. In U.S. Pat. No. 4,192,587, it is intended that a selected ratio of ambient to flash exposure light can be achieved from one exposure to the next over a determined range of camera-to-subject distances when the ambient light is above a certain level.
In U.S. Pat. No. 4,192,587 a diaphragm shutter defines a varying progression of exposure apertures, and the strobe flash unit produces a relatively constant amount of flash light. To provide a selected ratio of ambient to flash exposure light, a control system is provided for varying the time at which the strobe is energized during an exposure interval in accordance with subject distance and ambient light intensity. Such apparatus is complex and adds further to the cost of apparatus for controlling a flash exposure.